Dewaxing and hydrodewaxing processes are employed in the refining industry to treat petroleum fractions having initial boiling points over about 350.degree. F. to improve their pour point. The improvement in pour point is generally effected by selective removal of normal paraffins. Since the pour point of liquid hydrocarbon fuels, e.g., diesel fuels, shale oil, lube oils and other light gas oil fractions, are strictly controlled, the pour point specification of such fuels must be met if such are to be employed in their intended use.
The need to reduce the pour point of petroleum fractions has resulted in the development of numerous dewaxing and hydrodewaxing processes wherein the pour points of petroleum fractions are reduced by selective removal of paraffinic hydrocarbons. Processes relating to dewaxing and hydrodewaxing are well known in both the patent and scientific literature. Such processes have employed crystalline aluminosilicates as catalysts. For example, see U.S. Pat. Nos. 3,140,249; 3,140,252; 3,140,251; 3,140,253; 3,956,102; and 4,440,991. Further, ZSM-type aluminosilicates have been disclosed for use in hydrocarbon conversion processes involving dewaxing. Representative patents include U.S. Pat. Nos.: Re. 28,398; 3,700,585; 3,852,189; 3,980,550, 3,968,024; 4,247,388; 4,153,540; 4,229,282; 4,176,050; 4,222,855; 4,428,826; 4,446,007. These and other patents disclose the use of various crystalline aluminosilicates as catalysts for dewaxing processes.
Although a large number of zeolitic materials have been disclosed as employable as catalysts for dewaxing and hydrodewaxing catalysts, the use of other microporus crystalline molecular sieves has not received significant attention. This lack of attention is attributable to the scarcity of molecular sieves other than crystalline aluminosilicates. One disclosure of a catalyst containing a crystalline silicate, as opposed to a crystalline aluminosilicate, is disclosed in U.S. Pat. No. 4,441,991.
The instant invention provides for catalytic dewaxing and hydrodewaxing of hydrocarbon feedstocks by contacting such with catalysts comprising titanoaluminosilicate molecular sieves, as hereinafter described.